The Supreme Court has ruled that an employee’s spousal pension benefit can be paid to his same-sex partner.

The case, Walker v Innospec Limited, relates to retiree John Walker, who worked for global chemical organisation Innospec between 1980 and 2003. Walker, who paid into the organisation’s occupational pension scheme during his working career, sought to clarify with Innospec in 2006 whether his same-sex partner would receive the pension scheme’s spouse’s pension in the event of his death.

Innospec refused the spouse’s pension because Walker’s service for the organisation pre-dated 5 December 2005, which was when the Civil Partnership Act 2004 came into force. The basis of the refusal relates to the Equality Act 2010, which provides an exception to general non-discrimination rules to state that it is lawful to prevent or restrict access to a benefit, facility or service to a person where the right to that benefit is accrued before 5 December 2005 or which is payable in respect of periods of service before this date.

Walker has lived with his partner since 1993. They applied for a civil partnership on 5 December 2005 and this was formally registered on 23 January 2006. Walker has since married his partner.

Under the rules of the pension scheme, if Walker had married a woman, upon his death she would receive £45,700 per annum in a spouse’s pension. Walker’s husband would instead be entitled to the statutory guaranteed minimum of approximately £1,000 a year.

In November 2011, Walker lodged a claim with the Employment Tribunal (ET), arguing that he had been discriminated against on the grounds of his sexual orientation. The ET found that Walker had been subjected to both direct and indirect discrimination, therefore it upheld his claim. The ET further stated that the exception paragraph in the Equality Act 2010 should be read in a way as to be compliant with the EU’s Framework Directive, which establishes a framework for equal treatment in employment.

Innospec appealed this decision and took the case to the Employment Appeal Tribunal (EAT). Although the EAT agreed with the ET with regards to the discrimination claim, it allowed the appeal, ruling that the Framework Directive did not have a retrospective effect to render unlawful inequalities based on sexual orientation that arose before the last date for its transposition. It therefore ruled that the exception in the Equality Act 2010 was not incompatible with the Framework Directive.

Walker appealed the EAT decision and the case was taken to the Court of Appeal, where it was dismissed. Walker then appealed to the Supreme Court.

The Supreme Court has unanimously allowed Walker’s appeal, ruling that the 2010 Act is incompatible with the EU Framework Directive and must be disapplied. The judgement states that Walker’s husband is entitled to a spouse’s pension upon Walker’s death, provided that they remain married. This would be calculated on all of Walker’s years of service at Innospec.

The secretary of state for work and pensions is listed as an interested party for Innospec in the case. The government has argued that giving retrospective effect to the Framework Directive would impose costs on pension schemes that may not have been taken into consideration in scheme funding assumptions.

Lord Kerr wrote in the judgement: “I would therefore hold that Mr Walker’s husband, provided he does not predecease him, and that they remain married at the time of Mr Walker’s death, is entitled under the Framework Directive to a spouse’s pension calculated on the basis on all the years of Mr Walker’s service with Innospec.”

Walker said: “I am absolutely thrilled at today’s ruling, which is a victory for basic fairness and decency. Finally this absurd injustice has been consigned to the history books, and my husband and I can now get on with enjoying the rest of our lives together.

“But it is to our government’s great shame that it has taken so many years, huge amounts of taxpayers’ money and the UK’s highest court to drag them into the 21st century. In the years since we started this legal challenge, how many people have spent their final days uncertain about whether their loved one would be looked after? How many people have been left unprovided for, having already suffered the loss of their partner?

“What I would like from Theresa May and her ministers today is a formal commitment that this change will stay on the statute books after Brexit.”

Emma Norton, lawyer at Liberty who represented Walker, added: “We are delighted the Supreme Court recognised this pernicious little provision for what it was; discrimination against gay people, pure and simple.

“But this ruling was made under EU law and is a direct consequence of the rights protection the EU gives us. We now risk losing that protection. The government must promise that there will be no rollback on [lesbian, gay, bisexual and transgender] rights after Brexit, and commit to fully protecting them in UK law.”

A government spokesperson said: “We are reviewing the implications of this judgement in detail and will respond in due course. The rights of same-sex couples have been transformed for the better since 2010 including the introduction of same sex marriage and legislation to ensure that pensions are built up equally for all legal partnerships.”